202
1.19.2.2.2.2 Trigger
Snapshot mode starts with a trigger. This can be either a hardware or a software signal.
The following trigger modes are available:
Mode Description
Continuous Free running, no external trigger signal needed.
OnDemand Image acquisition triggered by command (software trigger).
OnLowLevel As long as trigger signal is Low camera acquires images with own timing.
OnHighLevel As long as trigger signal is High camera acquires images with own timing.
OnFallingEdge Each falling edge of trigger signal acquires one image.
OnRisingEdge Each rising edge of trigger signal acquires one image.
OnHighExpose Each rising edge of trigger signal acquires one image, exposure time corresponds to pulse
width.
OnLowExpose Each falling edge of trigger signal acquires one image, exposure time corresponds to pulse
width.
OnAnyEdge Start the exposure of a frame when the trigger input level changes from high to low or from
low to high.
See also
For detailed description about the trigger modes ( https://www.matrix-vision/manuals/ [mv←-
IMPACT Acquire API])
• C: TCameraTriggerMode
• C++: mvIMPACT::acquire::TCameraTriggerMode
1.19.2.2.2.3 Erase, exposure and readout
After the trigger pulse, the complete sensor array is erased. This takes some time, so there is a fix delay from about
285 us between the trigger pulse on digital input 0 and the start of exposure of the first line.
The exact time of exposure start of each line (except the first line) depends on the exposure time and the position of
the line. The exposure of a particular line N is finished when line N is ready for readout. Image data is read out line-
by-line and transferred to memory (see: https://www.matrix-vision.com/tl_files/mv11/←-
Glossary/art_rolling_shutter_en.pdf).
Exposure time is adjustable by software and depends on the image width. To calculate the exposure step size you
will need following formula:
LineDelay = 0
PixelClkPeriod = 1
--------
PixelClk
RowTime = ( ImageWidth + 244 + LineDelay )
*
PixelClkPeriod
RowTime = MinExposurTime = ExposureStepSize
Image data is then shifted out line-by-line and transferred to memory.
To calculate the maximum frames per second (FPS
max
) in snapshot mode you will need following formula:
FrameTime = (ImageWidth + 244)
*
((ImageHeight + 16) / PixelClock)
FPS_max = 1
-----------------------------------
FrameTime + ExposureTime
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